The introduction of advanced video applications such as digital television, high-definition television, and internet-based video has prompted the need for standardizing compression technologies for use in television broadcast and home entertainment systems. For example, the International Standards Organization's (ISO) Motion Picture Experts Group (MPEG) developed the MPEG4 compression standard to support internet-based video applications. In another example, the Video Coding Experts Group (VCEG) of the International Telecommunication Union's Telecommunication Standardization Sector (ITU-T) developed the ITU-T H.263 compression standard to support videoconferencing applications. These and other video coding standards are being developed to enable wide utilization of new video technologies in commercial and personal settings. In 2001, the Joint Video Team (JVT) was formed to develop a full international standard that offered significantly better video compression efficiency for low bit-rate visual communication systems. To achieve its goal, the JVT brought together experts from ISO MPEG and from ITU-T VCEG. The proposed outcome of this joint effort was to result in two separate but technically consistent standard specifications: the ISO MPEG4 Part 10 and the ITU-T H.264.
The H.264 coding standard provides flexibility by defining a baseline profile, a main profile, and an extended profile in order to serve a variety of applications. The main profile, for example, is intended to support digital television broadcasting and next-generation digital versatile disk (DVD) applications. The baseline profile, for example, is intended to support mobile applications that may have limited processing capabilities. The extended profile, for example, is intended to support streaming video and may comprise features that provide error resilience and that facilitate switching between bitstreams.
Enhancements to the H.264 coding standard have resulted from a new set of coding tools known as the fidelity range extensions (FRExt). The FRExt extensions, for example, are intended to support high image resolutions needed in applications such as studio video editing, post-production processing, standard definition (SD) and high-definition (HD) television, and enhanced DVD video. The FRExt extensions also define a high profile, which may be utilized to provide higher coding efficiency without adding significant implementation complexity. In this regard, the high profile may be adapted by applications such as those supported by the Blu-ray Disk Association, the digital video broadcast (DVB) standards, the HD-DVD specification of the DVD Forum, and/or the new broadcast TV specification of the US advanced television systems committee (ATSC).
In the profiles defined by the H.264 coding standard, coding or compression of image and/or video signals may be accomplished by first transforming the signal, or an error that may result from predicting the signal, from a spatial domain representation to a spatial frequency domain representation. For example, image and/or video signal compression may be achieved by means of a two dimensional (2D) Discrete Cosine Transform (DCT). Another transformation approach may be to adaptively change the basis functions in a 2D transform based on signal content. In this latter approach, for example, the 2D transform may be based on wavelets. Following the transformation operation, a quantization step may be utilized to zero-out any coefficients with relatively low values. The transformation and quantization steps may reduce redundancies in the signal's spatial content by compacting the signal's energy to as few basis functions as possible. By increasing the size of the transform, a corresponding increase in signal energy compaction may be achieved thereby improving the performance of the entire compression system.
However, increasing the transform size in order to achieve the type of low bit-rate system envisioned by the JVT may result in compression artifacts that may be clearly visible upon displaying the signal after decompression or decoding. These artifacts may be particularly noticeable in areas of sharp transitions such as high contrast edges in image and video signals. In certain applications, such as those supported by the high profile for example, other approaches may be necessary to achieve lower bit-rates, that is, to provide higher coding efficiency, without producing compression artifacts that may result when large transform sizes are utilized in portions of the image and/or video signals that exhibit sharp or abrupt transitions.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.